Add support for processing test contexts ahead-of-time

[snicoll]

Overview

Now that we can process an application context for AOT optimizations, we'd like to extend that feature by providing support in other parts of the portfolio. One that we have experimented with in Spring Native is processing the application contexts that the TCF uses for a module so that they are "native-friendly".

In practice, this would mean introducing something like TestContextAotProcessor that builds on top of ApplicationContextAotProcessor, pre-processing the test infrastructure for each context identified amongst a set of test classes.

We'd need at least one additional context to provide a "prepared" GenericApplicationContext for a MergedContextConfiguration as each "bootstrapper" can have its own logic baked in.

Related Issues

• Introduce TestClassScanner to locate Spring test classes for AOT processing #28824
• Introduce AotContextLoader SPI in the TestContext framework #28906
• Add support in the TCF to use pre-processed AOT contexts #28205
• Introduce command-line application for triggering AOT test context processing #28825